The Conjurer was a named that the spell caster the Bumbling Conjurer transitioned to after he gained more experience.
The Conjurer seems to rival the abilities of the Warlock name. It is able to accomplish feats akin to the Warlocks destruction allowing the named to cause the mountains to fall.
The role of the conjurer is to intentional execute skillful magical acts. Unlike the bumbler which seemed to accidental cause mass chaos on a battlefield the conjurer is able to execute precise magical actions through years of practice as well as much wider vast of knowledge.
The name greatly augments the users capacity for magic as well as the mages capacity for spells. Whereas the bumbler was limited by knowledge and thus would accidental use spells that it had no knowledge of causing them to sometimes backfire. The Conjurer has a wide breath of both knowledge and skill in which to use the spells.